Automatic voltage-regulator.



Gr A. BURNHAM. AUTOMATIC VOLTAGE REGULATOR. APPLIGATION FILE-I) JULY 16,1910; gmmwlzn'oo'r. 10, 1914.

1,1 18,633, Patented Nov. 24, 1914.

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- GEORGE A BURNHAM, OF CLIFTONDALE, MASSACHUSETTS.

AUTOMATIC VOLTAGE-REGULATOR.

Application tiled Ju1y'16, 1910, Serial No. 572,314. Renewed October Toall'wkom it may concern Be it known that I, GEORGE A. BURN- HAM, acitizen of the United States, and resident of Cliftondale, in the countyof Essex and State of Massachusetts, have invented an Improvement inAutomatic Voltage-Regulators, of which the following description, inconnection with the accompanying drawings, is a specification, likeletters on the drawings representing like parts.

To regulate the terminal voltage of gen- ,the field current, and thishas been accomplished by means of interrupting the field circuit of thegenerator, or by excluding and including periodically an additionalfixed resistance in series with the usual field resistance.

lVhen the entire field circuit is opened a. powerful change of fieldstrength is effected and vicious sparking or arcing results from thefield discharge which renders these methods too heroic to besatisfactory in practice, and they have not therefore proven successful.When a fixed resistance in series with the field winding is employed theregulating devices must be of a character which will permit a delicateresponse'to the conditions of the external circuit, otherwise theregulating parts will overshoot the proper degree of. movement and failin their intended effect in maintaining constant voltage.

My invention is designed to effect as prompt'and sensitive a regulationas either method could afiord without incurring the deleterious arcingfrom sudden and great changes of field strength and without incurringjerky and irregular regulator movements; I effect this by employing amakeand-break device constantly operating to shunt a moderate fieldresistance, said device constantly operating under powerful magneticcontrol which is extremely sensitive to minor voltage variations, and Iprovide a hand-switch for adjusting thefield resistance to permit it toact to best advantage under wide ranges of load in the'main circuit.Also I secure quick action 'for varying-the proportion of the make. withrelation to the break, in the make-and-break device, by providing meansindependent of the voltage being regulated to coiiperate with thevoltage-responsive mechanism in a giving the make-and-break deviceextreme Specification of Letters Patent.

it is usual to vary the strength of I ness and quickness of PatentedNov. 24, 1914.

16, 1914. Serial No. 867,035. sensitiveness. The make-and-break devicepreferably consists of two contact members, one of which is responsiveto two separate influences, one the changes in voltage in the maincircuit which is being regulated, and the other independent of saidchanges in voltage. Preferably the make-and-break de vice is of the typein which one member contains a. conducting section and an ins ulatedsection and is rotary, or at least continuously movable, at practicallyconstant speed, and the other member has continuous vibratory movementwith relation to said movable or rotary member, and I provide mechanismfor varying the throw or vibration thereof, consisting of two separatemeans, preferably comprising an electromagnetic actuator and aquick-acting actuator, such as a spring, ooiiperating with saidelectromagnetic actuator to give stea dimake-andbreak action and toprevent tendency of the vibrating member to overthrow or to be moved bythe mechanism.

In the drawings, I have shown diagrammatically a preferred embodiment ofthe invention.

For convenience of illustration, I have shown a generator 1 whose mains2, 3 supply lamps or other translating devices 4. The field 5 of saidgenerator is under the control of a rheostat or variable resistance 6,such as usually employed for regulating the voltage of a generator orthe speed of a motor. The form of make-and-break device herein showncomprises a rotary cylinder 7 divided diagonally into a conductorsection 8 and an insulated section 9, said cylinder being rotated anysuitable means, as by a motor 10, lterein shownf as supplied with energyfrom any suitable source, as for convenience supplied from the mains 2,3by conductors .11, 12. Cooperating with the cylindrical contact member7 is a brush contact 13 whose vibrating arm 14: is pivoted at 15. An-arm16 therefrom is connected at'l7 to the core 18 of an electromagnet whosewinding19 may be supplied IL with energy from any source of power, shownfor convenience as -connected to the mains 2-, 3 by wires 20, 21-, aresistance 22 being interposed in the wire 21. A spring 23 normallytends to overpower the electromaghet when deener'gized or to hold thecontact arm 14in opposition to the electromagnet, and a dash=pot 24 ispreferably provided to prevent too great an amplitude of movement of thearm 151 under the influence of said spring. A contact-making voltmeterserves to control the electromagnet, being herein shown as comprising anelectromagnet 25 connected across the mains by conductors 26, 27 (aresistance 28 being interposed in the latter), the core 29 of saidelectromagnet operating a contact lever 30 pivoted at 31 and having amovable contact 32 to cooperate with a fixed contact 33 connected by awire 34: to the conductor 21, the conductor 20 being connected by ayvire35 tosaid lever, preferably at the pivot 31 and said lever Qbeingnortnally held in practically floating or balanced position by a spring36 so as to have extreme sensitiveness of make-and-break a'ctlon' 1nresponse to its electromagnet 25. make-and-break ac tion opens andcloses a short circuit for the brush operating, coil119, providing apowerhi1 and sensitive adjustment for the brush which makes its actionreliable under the drag of the rotary interrupter 9. Cooperating withthe rotary contact member 7 is a brush 37 connected by a wire 38 to thearm 35,

39 ofthe rheostat, the other terminal of the rheostat being connected bya wire 40 to the conductor arm 1 1 of the vibrating contact member, anda condenser 41 being connected across the wires 38, 40. The condition ispreferably such that when the voltage is constant in the main linecircuit, the contact-making portion of the volt-meter, i. e. the lever30, is floating, by which I mean that the'contacts 32, 33 are in such asensitive or balanced relation that they may be said to be open or to beclosed, as either relation may then exist. The result is that the arm 14is maintained in a constant state of vibration as the cylinder 7rotates. It now the load 4 isincreased so that the voltage lowers in themain circuit, the contact 32 will be maintained closed, therebydemagnetizing the electromagnet 19, whereupon the spring 23 instantlytends to shift the brush 13 to the left thereby momentarily increasingthe duration of shortcircuit of the rheostat in the field circuit of thegenerator, which increases the current in the field and raises thevoltage in the main circuit,and when said voltage reaches normal thecontacts 32, 33 open, thereby energizing the electromagnct 19 and movingthe brush '13 back to the right in opposition to the spring 23 anddashpot 24. This causes the i eostat tobe short circuited for a shorterthe generator duration at each rotation of the cylindrical contactmember 7. The constant vibration in the main circuit maintains acorresponding constant vibration of the brush 13.

It is awell known fact that the current cannot rise instantly in thefield circuit of Consequently the arm 14 would move too far or overreachits proper position it said arm were equally balanced or floating, aswould be the case if the arm were dependent for all itsmovement simplyon the energizing and deenergizing of electromagnetic control, andaccordingly to give quickness, sensitiveness, and accuracy of movementand prevent the efiect of this oven-caching or tendency to overreach, Iprovide the spring 23 (and preferably the dash pot 21) which tends atall times to move the brush 13 and arm 14 to the left so as to givequickness in overcoming their movement to the right. This prevents thebrush from remaining in the overreaching position (as it otherwise wouldfects, the latter being the well-known pumping eifects, commonlyexperienced with one solenoid only which is energized directly from themains. By my combination, I establish a vibration, which,notwithstanding that its maximum in either direction extends to theimproper position of the brush, is so quick in action that itsover-reaching effect is practically lost or eliminated (because of itsquickness of movement and the magnetic sluggishness of the field) andthe operative influence thereof is simply that of the mean orintermediate half. The arm 14 and its brush are vibrated constantly eventhough the voltage is at normal, but inasmuch as the return movement isrendered quick and instantaneous by the spring 23 the resultant currentin the field is not determined by either of the extreme positions of thebrush but by the intermediate or average position. If the entire backand forth movement of the brush were determined solely byelectromagnetic operating or shifting. means, the time required tomovethe brush would be dependent uponthe comparatively long length of timerequired for energizing and deenergizing theelectromagnetic means, whichis necessarily slow because of inductance and also because of the timerequired for the voltmeter to operate.

on account of its inductance.

WVhenever there is a change of voltage in the main line, the contacts32, 33 either remain closed or remain open until the voltage has beenrestored in the main line. This re sults in changing the position of thebrush 13 lengthwise of the cylinder 7 or in other words changes involtage in the main line cooperate with the normal vibratory movementabove explained, to produce a variable vibration or variable length ofvibration and also to cause the brush 13 to assume said differentpositions longitudinally of the contact member 7, thereby varying theduration of the break with relation tethe duration of the make in themake and break device.

In further explanation of the importance of myinvention, I secureaccuracy by employing the voltmeter therefor and power by employing theelectromagnet therefor, as

distinguished from attempting to provide both accuracy and power bymeans of the same electromagnet (still greater accuracy being secured bycombining a spring action with-the power actuating electromagnet, asalready explained), in connection with the continuous short circuitingof the field rheostat. By

short circuiting this adjustable rheostat 'I eliminate the vicious anddestructive sparking and also bring the intensity of sparking'under thedirect control of theoperator, as already explained.

Having described my invention, what I claim as new and Patent is,

In a voltage regulator, the combination of a generator having a shunt.field, a constantly operating motor-driven interrupter in a shuntaround a portion of the field resistance, said interrupter having anoblique cylindrical contact to effect a" variable interdesire to secureby Letters val of the shunt closure, a voltage magnet GEORGE A. BURNHAM.

WVitnesses:

GEO. H. MAXWEL EDWARD MAXWELL.

Copies of this patent may be obtained for five cents eacli, byaddressing the Commissioner of Patent Washington, D. C.

